Two or more users may want to meet on a specific geographical position at a specific time instant, such as e.g. at the current location of one of the users. It may however be difficult for the users to determine and locate the specific geographical position where the meeting is to take place e.g. the current location of another user. Also, it may be a problem to determine the own geographical position, in order to navigate towards the agreed specific geographical position.
A known possibility to determine the geographical position of a user equipment is to use satellite based positioning methods. Due to their high accuracy of tracking the position of a user equipment, satellite based positioning methods, such as those based on the Global Positioning System, GPS or on the European Galileo system, are gaining popularity. However, due to invisibility of satellites in closed areas, this method can typically only be employed in open or quasi-open area environments. Also, a GPS or any other satellite based method is specified as a user equipment capability. This means that low-end terminals are not likely to offer satellite based positioning services. Thirdly, the GPS based method was introduced in later releases in widely used wireless communication standards, such as the 3GPP UTRAN. Similarly, the early release of 3GPP Long Term Evolution (LTE) does not contain the GPS positioning method. Thus, legacy terminals or terminals compliant to early standards releases cannot be expected to support GPS based services.
The standards for existing and future generation cellular communication systems provide support for location based and positioning services. Traditionally, these services are based on determining the geographical position of user equipments relative to base stations (node Bs) in the coverage area of a Radio Access Network (RAN) and/or a Public Land Mobile Network (PLMN).
Determining the geographical position can be based on path loss measurements and reporting that allow the serving base station to calculate the geometry of the served user equipments. Once the geometry is established, Node Bs can estimate the geographical position by, for instance, using pre-established data bases that associate geometry values with geographical positions/spatial coordinates. The pre-established data bases may have been obtained during measurement campaigns.
A well known specific example is that of the so called location fingerprinting positioning method. It is based on the creation of a radio fingerprint based on path loss or signal strength measurements for each point of a fine coordinate grid that covers the Radio Access Network. The fingerprint may e.g. consist of the cell identities (cell IDs) that are detected by the terminal, in each grid point and/or quantized path loss or signal strength measurements, with respect to multiple radio base stations, performed by the terminal, in each grid point.
According to the known location fingerprinting positioning method, a radio fingerprint is first measured, after which the corresponding grid point is looked up and reported, whenever a position request arrives.
Determining the position of the user equipment can also be based on measuring the time difference of arrival of some known signals, such as pilot symbols, from serving cell and any one of the neighbour. The user equipment may perform this measurement with respect to several neighbour cells, typically three or four cells, to collect reliable statistics for determining its position. One specific example is the observed time difference of arrival between the received primary CPICH from the serving cell and the neighbour cell. This measurement is used in WCDMA. It is more specifically termed as the observed System Frame Number (SFN)-SFN time difference type 2. In such systems, the user equipment can track its positions by measuring SFN-SFN time difference type 2. The accuracy of this measurement is two times better than other similar timing measurements in WCDMA e.g. SFN-SFN type 1, which is measured on broadcast channels from serving cell and neighbour cells. Another difference is that SFN-SFN type 2 does not require the user equipment to synchronize to the broadcast channel of the neighbour cells. On the other hand the user equipment is synchronized to the pilot symbols, e.g. primary CPICH in WCDMA of the N strongest neighbour cells for performing measurements. Due to these reasons SFN-SFN type 2 or similar measurements, based on pilot symbols, are more suited for determining the user equipments position.
It is thus a need for a service that can provide assistance to users who try to find the way to another user, or to any other determined meeting place. In this document, such service will be referred to as a rendezvous service.
In order to achieve such rendezvous service to assist the involved users, the position of the own user equipment and/or the other user equipments are determined.
For example, user equipment A provides his GPS coordinates to user equipment B who in turn uses a “GPS map” to calculate a route and navigate from his current position to user equipment A's position.
However, this type of service assumes that user equipment A can determine its own GPS coordinates and communicate them to user equipment B. If user equipment A does not have a GPS equipment, the rendezvous service is difficult to provide, since the geometry based positioning is less precise and more difficult to provide to user equipment “B” who may not have the same coordinate system. User equipment B can e.g. be served by another PLMN than user equipment A.
Thus it is a problem to provide a high precision (“GPS like”) rendezvous service for user equipments that do not have a GPS receiver and/or that cannot determine position by satellites due to invisibility of satellites in closed areas.
Generally, the problems associated with providing a high precision rendezvous service are to obtain the GPS coordinates of a user equipment without a GPS receiver/out of satellite range and/or to be able to navigate to a certain location with a user equipment without a GPS receiver and a GPS map.
Further, the problem as formulated above is not addressed by existing standards and state of the art solutions. On the one hand, traditional cellular devices such as e.g. GSM do not aim at providing GPS based navigation and positioning services. Rather, these devices generally provide positioning services based on relative coordinates typically valid within a public land mobile network (PLMN), i.e. relative to the position of cellular base stations or sites. On the other hand, positioning and location based services making use of the GPS coordinates are provided for devices with GPS receiver fulfilling, for instance, the relevant 3GPP specifications.
Shortly put, the problem with state of the art solutions is that they do not provide a solution to the problem described in the preceding paragraphs.
An example of such a situation is when a first user, who may be equipped with a GPS receiver and a GPS map, wishes to meet a second user at the current location of the second user with a legacy user terminal, without any GPS support. For instance, the first user would like its terminal screen to display the location of the second user. This not only requires the acquisition of the current location or geographical coordinates of the first user but also its permission for security/integrity reasons.
That is, generally speaking, the problem is to provide rendezvous service to users some or all of which not having a GPS device.